This is my opinion...
How many people have the cross over installed? It sounds like very few people. And there are a substantial number of people who have reported no noticeable difference, and there are some that can tell a difference.
Are there certain engine years that make the difference? Or maybe climate? Or maybe fuel? Or maybe from a mod? Or maybe from the type of oil?
Does International run a cross over? Are fleets being converted?
Do the newer engines have a cross over?
There are no claims of performance improvement or longevity. For some engines, it might improve the sound the injectors make.
So why spend the extra $$$?
Why take the unnecessary risks?